1. Field of the Invention
The present invention relates to a sealing device suitably used in a shaft seal part having a large shaft eccentricity or a large mounting eccentricity, for example, a dust seal or the like of a steering shaft in a vehicle such as a motor vehicle or the like, and more particularly to a sealing device with a sound insulating seal having a sound insulating function in addition to a sealing function. The sealing device in accordance with the present invention is used in a general purpose machine or the like in addition to the vehicle mentioned above.
2. Description of the Conventional Art
Conventionally, there has been known a sealing device 51 with a sound insulating seal shown in FIG. 3, and it is structured as follows. The sealing device 51 in FIG. 3 is constituted as a steering dust seal for a vehicle (refer to FIG. 5 described in Japanese Unexamined Patent Publication No. 9-242880, Japanese Unexamined Utility Model Publication No. 6-84068, FIG. 3 in Japanese Unexamined Patent Publication No. 11-82752, Japanese Unexamined Patent Publication No. 11-351385).
First, there is provided a seal body 56 sealing a clearance 55 between a peripheral surface 53a of a shaft hole 53 provided in a front dash panel 52 corresponding to a housing and a steering shaft 54 corresponding to a shaft inserted to the shaft hole 53, and a sound insulating seal 57 insulating a transmitted sound such as an engine sound transmitted to a passenger room inner side B from an engine room side A through the clearance 55, a traveling sound or the like is assembled in the seal body 56.
The seal body 56 has a mounting part 58 mounted to an inner periphery of the shaft hole 53 of the front dash panel 52, and a seal lip part 59 brought into contact with a peripheral surface of the steering shaft 54, and a bellows part 60 for responding to the shaft eccentricity or the like is integrally formed between the mounting part 58 and the seal lip part 59.
Further, the sound insulating seal 57 has a sound insulating member 61 fixed to an inner peripheral side of the mounting part 58 of the seal body 56, and the sound insulating member 61 is formed, for example, in an annular shape by an elastic body.
The sealing device 51 mentioned above is structured such that the sound insulating member 61 of the sound insulating seal 57 arranged at the passenger room inner side B achieves a sound insulating function with respect to the transmitted sound transmitted through the bellows part 60 of the seal body 56 formed in a thin shape by an elastic body, thereby reducing a noise level at the passenger room inner side A, however, the following problems are generated with respect to the sound insulating performance which can be achieved thereby.
The sound insulating member 61 of the sound insulating seal 57 mentioned above is fixed to an inner peripheral side of the mounting part 58 of the seal body 56 in accordance with a fixing means or the like, and a large clearance (a diametrical clearance) 62 is set at a further inner peripheral side thereof, with respect to the steering shaft 54. Accordingly, the transmitted sound through the bellows part 60 mentioned above passes through the clearance 62 (as shown by an arrow C), whereby the achievable sound insulating performance is limited.
In order to solve the problem mentioned above, the applicants of the present application have proposed a sealing device 61 in which two seal bodies 62 each having a mounting part 63, a seal lip part 64 and a bellows part 65 are arranged side by side so as to form a bellows double structure, as shown in FIG. 4. In accordance with the sealing device 61, since the seal lip part 64 of the seal body 62 at a passenger room inner side A is brought into contact with a steering shaft and the clearance in the diametrical direction is not formed at an inner peripheral side thereof, it is possible to increase the sound insulating performance (refer to FIG. 1 in Japanese Unexamined Patent Publication No. 9-242880, FIG. 1 in Japanese Unexamined Patent Publication No. 11-82752).
However, in accordance with this prior art, as a result of the double structure obtained by arranging two seal bodies 62 side by side, a length in an axial direction of the whole of the sealing device 61 (a width of a product) can not help being increased. Accordingly, there is room for further improvement in this point.